This invention generally relates to a composition having co-continuous interconnecting channel morphology comprising three componentsxe2x80x94two polymers (i.e. components A and B) and a particle (i.e. component C) wherein the channels consist mainly of component B and the majority of component C resides in the channels. Components A and B are generally immiscible within each other. In addition, one criteria for selecting component C and components A and B may be based on component C preferential affinity for component B over component A. Another criteria for selecting component C may be based on the capacity of component C to absorb and/or release a desired substance. For example, component C may be an absorbing material such as desiccant. In one embodiment, the composition of the present invention is useful in the manufacture of shaped articles such as containers and packaging for items requiring controlled environments.
There are many items that are preferably stored, shipped and/or utilized in an environment that must be controlled and/or regulated. For example, in the moisture control area, containers and/or packages having the ability to absorb excess moisture trapped therein have been recognized as desirable. One application in which moisture absorbing containers are desired is for the shipment and storage of medications whose efficacy is compromised by moisture. The initial placement of medicines into a sealed moisture free container is usually controllable. Furthermore, the container for the medicine is selected so that is has a low permeability to moisture. Therefore, the medication will normally be protected from moisture until it reaches the end user. Once the medicine is received by the customer, however, the container must be repeatedly opened and closed to access the medication. Each time the container is opened and unsealed, moisture bearing air will most likely be introduced into the container and sealed therein upon closure. Unless this moisture is otherwise removed from the atmosphere or head space of the container, it may be detrimentally absorbed by the medication. For this reason, it is a well known practice to include a desiccating unit together with the medication in the container.
Other items, electronic components may require reduced moisture conditions for optimal performance. These components may be sealed in containers, but excess moisture that is initially trapped therein must be removed. Furthermore, the housings may not be completely moisture tight, and moisture may be allowed to seep into the container. This moisture must also be retained away from the working components. For these reasons, it is important to include a desiccating agent within the housing for absorbing and retaining excess moisture. Because of the delicacy of many of the components that are to be protected from the moisture, it is important that the desiccant used not be of a xe2x80x9cdustingxe2x80x9d nature that may contaminate and compromise the performance of the components. Therefore, it has been recognized as advantageous to expose a desiccating agent to the interior space of such containers, while at the same time shielding the working components from actual contact with the desiccating material, including desiccant dust that may be produced therefrom.
In other instances, moisture may be released from items that have been placed in containers or sealed in packaging wrap for shipping and/or storage. Prime examples of such items are food stuffs-that release moisture during shipping and storage. In the instance of containers that are sealed and substantially impermeable to moisture, the released moisture will remain within the container. If not removed, this released moisture may have ill effects on the very item that released the moisture. It has been found that a substantial amount of moisture is released from certain food products within the first forty-eight (48) hours after manufacture and packaging. This released moisture will remain until removed. If the moisture is not removed shortly after its release, it may cause the food to degrade into a condition that is not saleable. In these cases, desiccants may be included together with the contained items to continually absorb the released moisture until the product is unpacked. In this way, a relatively dry environment is maintained about the stored item.
The present invention discloses a composition having co-continuous interconnecting channel morphology. In one embodiment, these co-continuous interconnecting channels communicate the particle, which is predominately residing in the channels, to the appropriate areas of the exterior of the composition in a manner that permits the desired property (e.g., gases and vapors) to migrate from either outside the composition to interior locations where the particle is positioned or from the interior locations where the particle is positioned to the environment. Furthermore, these co-continuous interconnecting channels through which the desired property is permitted to travel are occupied by a polymer (e.g., hydrophilic agents) that control the percolation through the composition. This polymer is drawn out into interconnected channels that contain a percolation path.